This invention pertains to vehicular and pallet transport and, more particularly, to methods and apparatus for the design and manufacturing of guideways for vehicles and pallets. The invention has application, for example, in track or guideway operated vehicular and pallet systems, e.g. in providing the operating guideway that defines the motion in an automation system. The invention has still more particular application, by way of non-limiting example, in linear motor propulsion guideways and/or guideways for magnetically guided vehicles.
Guideways currently in use are installed on site from their several individual components. These may provide guidance, propulsion, position sensing, communication and running surfaces for vehicles or pallets. For example, an electric train has rails that provide guidance and a running surface. It also has a separate overhead structure or third rail that can provide power. Also, there may be sensors near the rails that indicate to a central location the position of the train. Guideways with so many individual components are expensive to produce, deliver, install, and maintain.
The individual components can be expensive, for example, since they often have features that require very accurate assembly and adjustment at the installation site. Designing and manufacturing these features so that they insure proper operation of the assembled units, yet, with sufficient leeway to facilitate assembly under field conditions add to the cost of the parts.
Delivery of a transport system to the site where installation is planned involves many precision parts and tools. Various applications for transport systems require the guideways to be installed in clean or dirty environments, indoors or outdoors. Great care must be taken to account for parts and tools. Packaging and shipping many individual pieces and fasteners are examples of added cost to the system.
Installation of a transport system is time consuming for both the installer and the customer waiting to use the system. Transport systems arrive at the site of the installation in many pieces to be built in a non-integrated, xe2x80x9cerector setxe2x80x9d fashion. A fastening method is needed for mounting each of the components that provides guidance, propulsion, position sensing, communication and/or running surfaces for the vehicles and/or pallets. Jigs and fixtures are needed to measure positional accuracy of the separate components to ensure that the system will work properly. If components are out of alignment, adjustments need to be made. Personnel that install the system must be knowledgeable of the many individual components that are required. This increases the cost and complexity of the system and adds to the time needed for guideway installation.
For example, a typical pallet transport system is currently belt driven. A transport system that utilizes a belt method of propulsion has many moving mechanical parts (i.e. rollers, tensioners, drive wheels, etc.). Installation of typical belt driven transport systems requires a significant amount of adjustment, tensioning, and fastening of components. In practice, much of this setup and installation adjustment is subject to the interpretation of the installing technician. It can be a nonspecific and highly unrepeatable process.
Routine maintenance of the transport guideways is required. Mechanical parts and components have an expected service lifetime. If, however, adjustment of the parts is needed for installation, then there is always the possibility that the adjustment may slip or change during the life of the transport system causing the need for increased maintenance to ensure safety and prevent failure. Even during planned, routine maintenance, if servicing the guideway requires a technician (or more) to dismantle, replace, fixture, and adjust an xe2x80x9cerector setxe2x80x9d of parts, the time necessary to remove the transport system from service while maintenance tasks are performed is significant, costly, and complex (especially if adjustments are needed).
An object of the invention is to provide improved methods and design of guideways for vehicular and pallet transport systems.
Another object of the invention is to provide such methods and apparatus as can be applied to linear motor propulsion and/or magnetic guidance systems.
Another object of the invention is to provide such methods and apparatus as can be applied to reducing the manufacturing cycle time, complexity and cost of linear motor propulsion.
Another object of the invention is to provide such methods and apparatus as can be applied to the reduction of cycle time, complexity and cost of the maintenance and installation of a linear motor propulsion guideway.
Another object of the invention is to provide such methods and apparatus as can be applied to the mechanical packaging of the components of a linear motor propulsion guideway so as to improve positional accuracy of the components.
Another object of the invention is to provide such method and design of a guideway switch for vehicular and pallet transport systems.
The invention integrates linear motor propulsion into a guideway module that contains any combination of: linear motor propulsion, vehicle guidance, position sensing, communication, and vehicle or pallet running surface subcomponents.
One aspect of the invention integrates a combination of one or more subcomponents for linear motor propulsion, vehicle guidance, position sensing, communication, and vehicle or pallet running surfaces during the manufacturing of the guideway module. A single manufacturing operation can be used to position, affix, and encapsulate the selected subcomponent(s) in a module or modules. For example, the component(s) can be designed to be located in a plastic injection mold, typically, a reaction injection mold (RIM), which allows the subcomponent(s) to be positioned, aligned, and encapsulated in a single manufacturing step that has only a several minute cycle time. In this manner positional accuracy among the relationship of the subcomponent(s) can be maintained within a small tolerance (on the order of 0.25 mm) while costs remain very low.
Subcomponents are designed for integration into the guideway, either as a single encapsulated module or as separate but integrated units, thereby reducing the need to manufacture and ship many individual parts, fixtures, and fasteners to the site where the transport system is being installed. For example, the motor stator iron is segmented into blocks for use in both straight and curved modules. These stator iron blocks mount to a backplate for support and preliminary alignment during manufacturing. In a process such as RIM, the mold, as it closes, precisely aligns the stator iron blocks using features designed into the surface of the stator iron blocks. Where subcomponents are encapsulated as a single unit, the use of a backplate can have other integrated features as well. For example, it can provide support for the guidance channels prior to encapsulating the guideway module. It can also provide strength for the subcomponents during the encapsulating process so that the parts do not have to be designed as precision stand-alone components, thus reducing the cost of the subcomponents.
In a modular design of the guideway, a single manufacturing process such as encapsulating the components in a molding process allows for minimal treatment of surface finishes of the parts. For example, a molding material such as urethane, or epoxy fills the space between the components, forming the guideway. This encapsulates the components. Material that is injection molded around the component s will take the shape of the component, even if it is irregular. Once molded, the parts are scaled from the environment so that painting and plating are not necessary. This lowers the cost of the system and reduces the need for special handling of parts. Manufacturing motor subcomponents in this manner also provides the parts with a tolerance accuracy from the molding process that is suitable for installation registration without the need for additional surface machining or other expensive finishing of subcomponent surfaces.
Another aspect of the invention is the product design methodology that allows for the transport system to also be manufactured as independent subcomponents that can be installed with no adjustment unlike such current systems as belt driven transport or pallet systems. For example, if an existing transport system already has a method of position sensing, then just the linear motor propulsion subcomponent can be manufactured and used as a replacement for the inadequate existing propulsion method. Using similar manufacturing techniques as the modular guideway, the stand-alone individual subcomponent has a low cost mechanical packaging that incorporates manufacturing efficiencies such as, built in features of highly repeatable dimensional tolerances, integrated mounting features possibly molded during a RIM process, and little or no secondary surface finish operations.
Also, a customer may require that due to existing constraints, subcomponents must be installed in a diffuse manner. The stand-alone subcomponent allows the configuration to change if needed. For example, in the case where a pallet in a transport system is very small (200 mm by 200 mm square), there may only be enough space underneath the pallet for linear motor propulsion and position sense. If a subcomponent for guidance is required also, it would have to be located along the side edge of the pal let (for instance a roller coaster separates propulsion and guidance by having a center chain pull the cars up the first hill while the guidance wheels are separate at the outside of the cars).
Another aspect of the invention is the improvement of the efficiency of the manufacturing process and of the resulting module by integrating the functions of the parts. For example, in mounting the stator iron to the backplate, if the contact area between the two parts is great enough and can be maintained during the manufacturing process, then the backplate will function as a heat sink for the linear motor propulsion. Dissipating heat in this manner increases motor efficiency and eliminates the need for additional heat sink parts and assembly. Using an encapsulating material such as urethane in a molding operation to bond the subcomponents together allows the module be very rigid, drawing from the strength of the encapsulant, the guidance components, and the backplate. The components function as a single composite structure. Another integration advantage is that the components can have a common ground for static dissipation. Transportation vehicles and pallets moving over the guideway module surface will tend to build up a static charge due to the vehicular or pallet motion. The running surfaces, for example, could be electrically bonded to other components or directly to a backplate, which in turn, could be connected to a common grounding bus for the transportation system. In this way, the vehicle or pallet can be prevented from building a static charge that could cause damage to cargo or other peripheral devices.
Another aspect of the invention is to improve the transport switch. At the point in the guideway where the vehicle or pallet must merge from one guideway into another and conversely where a vehicle or pallet must diverge from one track to another, a section of guideway is needed that has the function of a switch. A switch requires additional subcomponents which cause the vehicle to follow the correct path enroute to a destination. The invention allows the integration of additional switching components into the modular guideway design. A switch guideway module, to the installation or maintenance technician, is not very different, except for shape, from other guideway modules.
Subcomponents for the switch are similar to other guideway modules, however there are also unique subcomponents that that facilitate the vehicle or pallet to move from one path to another. These subcomponents are integrated during the time of manufacturing. For example, using linear motor propulsion with any combination of one or more subcomponents, active guidance and power switching electronics can be encapsulated in the guideway module. This type of switch eliminates moving parts. It also simplifies the switch installation, and lowers the cost of the system. Integrating these specialized components into the guideway module reduces installation setup, training, maintenance, and complexity.
Another aspect of the invention is an integrated thermal expansion joint. Under various environmental conditions and routine use of the linear motor propulsion, temperature changes occur that cause the guideway subcomponents to expand and contract slightly (on the order of less than 5 mm for a 1.5 m guideway module). Features designed into the manufacturing process of the motor can allow a connection to be made from one guideway or one subcomponent of a guideway to the next based on the mounting requirements of the particular application of the guideway.